Hyginus was Pope for four years between 138 and 142. He succeeded Telesphorus following the latter's martyrdom under either Hadrian or Antoninus Pius. He was an Athenian Greek and some sources suggest he was a philosopher before his pontificate but modern scholars including J P Kirsch1 think this is a confusion with a Latin author of the same name. Hyginus is listed as a martyr but it is thought this is through tradition and there is no evidence to support this. His saint day is celebrated on 11 January.
The Liber Pontificalis states that Hyginus "organized the hierachy and established the order of ecclesiastical precedence (Hic clerum composuit et distribuit gradus)"1 however Duchesne states that this probably relates only to the lower orders of the clergy and Henry Wace claims that the decretals asigned to Hyginus were "spurious"2. There were two other "spurious" decretals, one supposedly instituting the tradition of godparents and the other decreeing that all churches should be consecrated.
It was during Hyginus' pontificate that the gnostics Valentinus and Cerdon were in Rome. They preached heretical ideas focussing more on the mystical nature of Christianity and Valentinus claimed that Jesus was not one with God but a higher being who would lead humanity to purification. Cerdon was the predecessor of Marcion who actually broke away and formed his own church. It is not really know how Hyginus dealt with these heretics however St Iraeneus states that Cerdon would recant and gain readmission to the church before erring again and being expelled. It is not know how many times this occured. What is certain is that Hyginus failed to eliminate this heresy as the gnostics were still present in the reign of Anicetus who died in 168.
Telesphorus - Pope - Pius I
1 - Catholic Encyclopaedia - http://www.newadvent.org/cathen/07593a.htm
2 - A Dictionary of Christian Biography and Literature to the End of the Sixth Century A.D., with an Account of the Principal Sects and Heresies - http://www.ccel.org/w/wace/biodict/htm/iii.viii.xxii.htm#iii.viii.xxiii